The present invention relates to a locking system for a thrust reverser of an aircraft turbojet engine, more particularly, such a locking system having at least one locking device on opposite sides of a thrust reverser door longitudinal center line.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan driven at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion from the turbojet engine, or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIGS. 1 and 2 illustrate a known pivoting door-type thrust reverser associated with the cowling of a turbofan-type turbojet engine. As illustrated in FIG. 1, the upstream portion of the cowling which defines the outer limits of the bypass flow duct and which is generally concentrically arranged about the turbojet engine (not shown) is designated as 1 and generally comprises an external cowling panel and an internal cowling panel interconnected by a frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of the bypass flow duct 15 through which the bypass flow air passes in the direction of arrow 14.
The cowling also comprises a thrust reverser, illustrated generally at 2, and a downstream cowling portion 3. The thrust reverser 2 comprises a door 7 pivotally attached to the cowling so as to pivot about transverse axis 17 such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position in which the forward end (towards the left as viewed in FIG. 1) of the thrust reverser door 7 is moved outwardly from the cowling, while a rear portion is moved inwardly into the bypass flow duct airstream so as to redirect at least a portion of the bypass flow through an opening in the cowling in a direction that has a reverse thrust component.
An actuator 8 for moving the door 7 between its forward thrust and reverse thrust positions may comprise a hydraulic cylinder extending through and mounted to the flame 6, and having an extendible and retractable piston rod connected to the thrust reverser door 7.
The thrust reverser door 7 has an outer door panel 9 and an inner door panel 11 joined together by an internal structure. The forward end of the door 7 may have a deflector 13 to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. When the door is in the forward thrust position, as illustrated in FIG. 1, the outer door panel 9 is substantially flush with the external surfaces of the upstream panel and the downstream fairing 3. The inner surface 11 tapers toward the outer surface 9 at the forward end of the door 7, forming cavity 16 when in the forward thrust position.
As illustrated in FIG. 2, a plurality of thrust reverser doors 7 may be incorporated into the cowling, such doors being circumferentially spaced around the periphery of the cowling. A portion 18 of the cowling extends axially between forward part 4 and the rear part 3 of the cowling adjacent thrust reverser doors 7 to provide structural rigidity to the cowling and to provide pivot mounting points for attaching the doors 7 to the cowling. French Patents 1,482,538 and 2,030,034 illustrate typical, known thrust reversers.
U.S. Pat. No. 3,605,411 discloses a pivoting door-type thrust reverser in which the deflector mounted to the upstream or forward end of the thrust reverser door is movable to an extended position when the door is in the reverse thrust position.
French Patent 2,618,853 discloses a thrust reverser in which the deflector is retracted when the door is in its forward thrust position to optimize engine performance.
In some applications, as illustrated in FIG. 1, the deflectors 13 project from the inner panel 11 of the thrust reverser door 7 even when the door is in its forward thrust position without extending into the bypass flow duct. This forms a cavity 16 facing inwardly into the bypass flow duct which will slightly degrade engine performance.
French Patent 2,680,547 discloses a thrust reverser having a combination of spoilers and deflectors to attempt to optimize the direction of exhaust flow.
Most door-type thrust reversers also have several different locking systems to keep the doors locked in their forward thrust positions, one such locking system being termed the primary lock. The primary lock is generally situated between the frame of the cowling adjacent to the front side of the reverse thrust opening and the forward edge of the door. The primary lock may be mounted either above the door actuator aligned with a longitudinal central axis of the thrust reverser door, or on one side or the other of the actuator offset from the central longitudinal door axis.
When the thrust reverser door is constrained by a central primary lock located along the longitudinal axis of the door, the door has a recessed housing to receive the actuator body within the thickness of the cowling structure. As a consequence, the cross section of the forward door portion is reduced, thereby lessening its structural rigidity.
When the thrust reverser door is in the forward thrust position, gas flow in the annular duct 15 exerts pressure on the inside surface 11 of the thrust reverser door 7. Because, as noted above, the thrust reverser door having reduced structural rigidity due to the location of the primary lock, the thrust reverser door may undergo more or less pronounced deformation depending upon flight conditions of the aircraft. Such pressure acting on the thrust reverser door can change the curvature of the thrust reverse door in the transverse direction thereby disengaging the door from the seal 5 at its forward edge degrading aerodynamic performance of the engine and aircraft, and reducing the door tightness.